In 40K, there is only war. That sums it up. War and then more war. Everyone is warring with everyone else. Period. Doesn't make a very tidy mmo setting, but thats the IP they chose.

Scale it down to 3 races. Do them right and make them as complete as possible. Add more races later as part of expansions. If they can make the game feel like a real extension of the IP, even if it doesn't include everything, then they will have captured something special and the game will only be stronger for it.

What GW/Vigil, and some of us are missing, is that they are not the only ones who own the lore. We have been telling this story over and over for 25 years. We voted on which aspects were cool and which weren't with our money (I voted for Squats). Those who wanted to play multiple races bought multiple armies because the lore said they wouldn't mix. You can't negate all that with a gimmick and expect everyone to buy it just because it has the almighy GW stamp of It's Profitable For Us At This Moment.

Under the Imperium of Man, I bet they have a SM class (tank), an IG (ranged dps), techpriest (healer), some sort of psyker (controller, buffer), and an inquisitor (rogue). Unfortunately that's WAR with guns. It may be fun for a while, but it will always have that forced, artificial feel and the sense that it should have been so much more.

They really watered down the lore for WAR, and I expect THQ/GW will do the same now with 40K. For example, in WAR Malekith and the Orc Warboss are just hanging out in the Chaos capital. Even if they are all "Destruction", they wouldn't be that cozy. I know they cut the Dark Elf and Orc cities, but Malekith and the Warboss should have at least been surrounded by their own armies. Malekith would never leave himself exposed, and only an idiot would let Orcs roam freely in his city.